A method for temperature measurement in a household appliance is described, for example, in German Patent DE 29 35 282 C2. In the known method, a processing unit of the household appliance generates a high-frequency electromagnetic excitation wave. The pre-defined transmit frequency is selected from a frequency band containing the temperature-dependent resonant frequencies that occur in an LC resonant circuit incorporated in a temperature measuring probe and which correspond to the temperatures expected at the temperature measuring probe during operation of the household appliance. During a first phase, the excitation wave is wirelessly transmitted to the LC resonant circuit of the temperature measuring probe. As a result, an electromagnetic response wave is generated in the LC resonant circuit, said electromagnetic response wave being wirelessly transmitted back to the processing unit during a second phase immediately following the first phase. The aforementioned process sequence is repeated continuously while increasing the transmit frequency in fixed frequency steps until the frequency band has been covered. The response waves received by the processing unit are converted to response signals. In an evaluation circuit of the processing unit, a pulse counter determines the temperature-dependent resonant frequency, and thus, the temperature at the temperature measuring probe. The known system has the disadvantage that LC resonant circuits are generally not suitable for use at high temperatures, such as around 250° C.
From DE 197 23 127 A1, it is known that surface wave devices can be used for temperature measurement in cooking zones of a cook top. There, the evaluation process provides for the temperature at the temperature measuring probe to be inferred based on the phase shift between the pulse patterns of the reponse signals. The same holds for the subject matter of German Patent Application DE 198 28 170 A1. Alternatively, German Patent Application DE 44 13 211 A1 proposes to evaluate the response signals by Fourier transformation.